Claims Analysis
Total Claims: 65
Claim 1
Independent Claim
114 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a spray head for outward projection of an irrigation water stream and supported for rotation relative to said housing; a rotary drive assembly for rotatably driving said spray head; a reversing mechanism including means for reversing the direction of spray head rotation, within the end limits of a part-circle arcuate path, said reversing mechanism including resilient means permitting forced spray head rotation beyond either one of said end limits to a rotational position outside said part-circle path and upon subsequent spray head rotation for automatically returning to reversing rotation between said end limits within said part-circle path.
Claim 2
Dependent Claim
114 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a spray head for outward projection of an irrigation water stream and supported for rotation relative to said housing; a rotary drive assembly for rotatably driving said spray head; a reversing mechanism including means for reversing the direction of spray head rotation, within the end limits of a part-circle arcuate path, said reversing mechanism including resilient means permitting forced spray head rotation beyond either one of said end limits to a rotational position outside said part-circle path and upon subsequent spray head rotation for automatically returning to reversing rotation between said end limits within said part-circle path.
Claim 3
Dependent Claim
30 words
The rotary drive sprinkler of claim 1 wherein said rotary drive assembly includes means for disengaging from driving relation with said spray head upon forced rotation of said spray head.
Claim 4
Dependent Claim
18 words
The rotary drive sprinkler of claim 1 including means for adjusting the arcuate spacing between said end limits.
Claim 5
Dependent Claim
168 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a spray head for outward projection of an irrigation water stream and supported for rotation relative to said housing; a rotary drive assembly for rotatably driving said spray head; and a reversing mechanism movable between forward- and reverse-drive positions for reversing the direction of spray head rotation, said reversing mechanism including a trip member for switching said mechanism between said forward- and reverse-drive positions, a first stop engageable with said trip member upon spray head rotation and shaped for moving said trip member to switch said mechanism upon spray head forward rotation and to permit trip member passage without switching said mechanism upon spray head reverse rotation, and a second stop engageable with said trip member upon spray head rotation and shaped for moving said trip member to switch said mechanism upon spray head reverse rotation and to permit trip member passage without switching said mechanism upon spray head forward rotation.
Claim 6
Dependent Claim
168 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a spray head for outward projection of an irrigation water stream and supported for rotation relative to said housing; a rotary drive assembly for rotatably driving said spray head; and a reversing mechanism movable between forward- and reverse-drive positions for reversing the direction of spray head rotation, said reversing mechanism including a trip member for switching said mechanism between said forward- and reverse-drive positions, a first stop engageable with said trip member upon spray head rotation and shaped for moving said trip member to switch said mechanism upon spray head forward rotation and to permit trip member passage without switching said mechanism upon spray head reverse rotation, and a second stop engageable with said trip member upon spray head rotation and shaped for moving said trip member to switch said mechanism upon spray head reverse rotation and to permit trip member passage without switching said mechanism upon spray head forward rotation.
Claim 7
Dependent Claim
34 words
The rotary drive sprinkler of claim 4 wherein said first and second stops comprise an arcuately spaced pair of stops having stop surfaces facing each other and ramped surfaces facing away from each other.
Claim 8
Dependent Claim
20 words
The rotary drive sprinkler of claim 5 including means for adjusting the arcuate spacing between said first and second stops.
Claim 9
Dependent Claim
16 words
The rotary drive sprinkler of claim 4 wherein said trip member comprises a resilient trip wire.
Claim 10
Dependent Claim
61 words
The rotary drive sprinkler of claim 4 further including a pop-up stem assembly having said spray head mounted thereon and movable between a retracted position with said spray head substantially within said housing and a spraying position with said spray head elevated above said housing, said rotary drive assembly being rotatably coupled to said spray head via said pop-up stem assembly.
Claim 11
Dependent Claim
27 words
The rotary drive sprinkler of claim 8 wherein said rotary drive assembly and said pop-up stem assembly move as a unit between said retracted and spraying positions.
Claim 12
Dependent Claim
243 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a spray head for outward projection of an irrigation water stream and supported for rotation relative to said housing; a rotary drive assembly for rotatably driving said spray head; reverse means movable between forward- and reverse-drive positions for reversing the direction of rotary driving of said spray head; a pair of arcuately spaced-apart stops defining the end limits of a part-circle path of spray head rotation, said stops having stop surfaces presented generally toward each other across said part-circle path and ramped surfaces presented generally away from said part-circle path; and a resilient trip member for switching said reverse means between said forward- and reverse-drive positions and extending to a normal position generally between said stops, said stops and said trip member being movable relative to each other upon spray head rotation to bring said trip member into engagement with said stop surfaces respectively at the opposite end limits of said part-circle path to switch the position of said reverse means to reverse the direction of spray head rotation; said trip member having sufficient resiliency to move beyond either one of said end limits upon forced rotation of said spray head to a position outside said part-circle path and subsequently to ride over either one of said ramped surfaces without switching the position of said reverse means thereby returning to said normal position between said stops.
Claim 13
Dependent Claim
243 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a spray head for outward projection of an irrigation water stream and supported for rotation relative to said housing; a rotary drive assembly for rotatably driving said spray head; reverse means movable between forward- and reverse-drive positions for reversing the direction of rotary driving of said spray head; a pair of arcuately spaced-apart stops defining the end limits of a part-circle path of spray head rotation, said stops having stop surfaces presented generally toward each other across said part-circle path and ramped surfaces presented generally away from said part-circle path; and a resilient trip member for switching said reverse means between said forward- and reverse-drive positions and extending to a normal position generally between said stops, said stops and said trip member being movable relative to each other upon spray head rotation to bring said trip member into engagement with said stop surfaces respectively at the opposite end limits of said part-circle path to switch the position of said reverse means to reverse the direction of spray head rotation; said trip member having sufficient resiliency to move beyond either one of said end limits upon forced rotation of said spray head to a position outside said part-circle path and subsequently to ride over either one of said ramped surfaces without switching the position of said reverse means thereby returning to said normal position between said stops.
Claim 14
Dependent Claim
28 words
The rotary drive sprinkler of claim 10 wherein said trip member comprises a resilient trip wire extending from said reverse means to said normal position between said stops.
Claim 15
Dependent Claim
49 words
The rotary drive sprinkler of claim 11 further including means for supporting said reverse means against rotation with said spray head, and means for supporting said stops for rotation with said spray head, said stops being movable into engagement with said trip wire upon rotation of said spray head.
Claim 16
Dependent Claim
18 words
The rotary drive sprinkler of claim 11 further including means for adjusting the arcuate spacing between said stops.
Claim 17
Dependent Claim
71 words
The rotary drive sprinkler of claim 13 wherein said adjusting means includes means for moving said stops to a full-circle adjustment position with their stop surfaces substantially in face-to-face relation and with said trip wire disposed beyond said end limits whereby said spray head rotates continuously through a full-circle path in either rotational direction with said trip wire riding over said ramped surfaces without switching the position of said reverse means.
Claim 18
Dependent Claim
27 words
The rotary drive sprinkler of claim 10 wherein said rotary drive assembly includes means for rotatably driving said spray head in a succession of small rotational steps.
Claim 19
Dependent Claim
61 words
The rotary drive sprinkler of claim 10 further including a pop-up stem assembly having said spray head mounted thereon and movable between a retracted position with said spray head substantially within said housing and a spraying position with said spray head elevated above said housing, said rotary drive assembly being rotatably coupled to said spray head via said pop-up stem assembly.
Claim 20
Dependent Claim
27 words
The rotary drive sprinkler of claim 16 wherein said rotary drive assembly and said pop-up stem assembly move as a unit between said retracted and spraying positions.
Claim 21
Dependent Claim
17 words
The rotary drive sprinkler of claim 16 wherein said drive assembly comprises a balanced ball drive assembly.
Claim 22
Dependent Claim
153 words
The rotary drive assembly of claim 10 wherein said spray head includes a nozzle having an orifice formed therein of selected size, and further wherein said rotary drive means includes a water-driven turbine; and further including water flow regulation means having at least one drive jet nozzle for passage of a first portion of the water connected to said housing into driving relation with said turbine and then to said spray head, a first bypass port including a pressure compensating valve, and a second bypass port including a flow control bushing with an open flow opening therein of selected size in accordance with the size of said spray head nozzle orifice, said first and second bypass ports being for bypass passage of a second portion of the water around said turbine to said spray head, said jet nozzle and said first and second bypass ports being in parallel flow relation with each other.
Claim 23
Dependent Claim
51 words
The rotary drive sprinkler of claim 10 wherein said rotary drive means comprises a water-driven turbine and wherein said reverse means comprises a swirl plate having at least two oppositely angled swirl ports formed therein for swirl passage of water in opposite directions for rotatably driving said turbine in opposite directions.
Claim 24
Dependent Claim
66 words
The rotary drive sprinkler of claim 20 including a jet nozzle for passage of a water jet into driving relation with said turbine, said swirl plate being disposed between said turbine and said jet nozzle and movable between a forward-drive position with one of said ports aligned with said jet nozzle and a reverse-drive position with the other of said ports aligned with said jet nozzle.
Claim 25
Dependent Claim
21 words
The rotary drive sprinkler of claim 21 further including means for limiting swirl plate movement between said forward- and reverse-drive positions.
Claim 26
Dependent Claim
117 words
The rotary drive sprinkler of claim 10 wherein one of said stops is carried by a drive ring rotatable with said spray head and the other of said stops is carried by a trip ring releasably carried by said drive ring, and further including means supporting said spray head and said drive ring for movement relative to said rotary drive assembly between a normal operating position with said trip ring rotating with said drive ring and an adjustment position with said trip ring locked against rotation with said drive ring, said spray head and said drive ring being rotatable relative to said trip ring when in said adjustment position to adjust the arcuate spacing between said stops.
Claim 27
Dependent Claim
20 words
The rotary drive sprinkler of claim 23 wherein said other of said stops is resiliently carried by said trip ring.
Claim 28
Dependent Claim
40 words
The rotary drive sprinkler of claim 23 further including lock means for locking said spray head and said drive ring in their normal position relative to said rotary drive assembly thereby preventing adjustment of the arcuate spacing between said stops.
Claim 29
Dependent Claim
17 words
The rotary drive sprinkler of claim 23 wherein said trip ring is ratcheted about said drive ring.
Claim 30
Dependent Claim
47 words
The rotary drive sprinkler of claim 23 further including a drive case for said rotary drive assembly and supported against rotation within said sprinkler housing, said trip ring and said drive case including interengageable means for locking said trip ring against rotation when in said adjustment position.
Claim 31
Dependent Claim
51 words
The rotary drive sprinkler of claim 27 wherein said interengageable means comprises at least one lug projecting outwardly from said trip ring and means forming a plurality of open slots in said drive case for receiving said lug when said spray head and said drive ring are in said adjustment position.
Claim 32
Dependent Claim
23 words
The rotary drive sprinkler of claim 23 further including means for biasing said spray head and said drive ring toward their normal position.
Claim 33
Dependent Claim
58 words
The rotary drive sprinkler of claim 23 wherein said spray head and said supporting means cooperatively define a generally annular recess when said spray head and drive ring are in said normal operating position, and further including a lock collar receivable into said recess to prevent movement of said spray head and drive ring to said adjustment position.
Claim 34
Dependent Claim
50 words
The rotary drive sprinkler of claim 23 wherein said spray head comprises a pop-up spray head also movable between a retracted position substantially within said housing and a spraying position extending above said housing, said spray head being movable between said normal and adjustment positions while in said spraying position.
Claim 35
Dependent Claim
90 words
The rotary drive sprinkler of claim 31 further including a drive case for said rotary drive assembly and supported against rotation within said housing, said supporting means comprising a generally cylindrical riser secured to and upstanding from said drive case, and a drive sleeve rotatably supported within said riser, said drive sleeve being rotatable with said drive ring and said spray head, said supporting means further accommodating limited axial shifting movement of said drive sleeve relative to said riser to permit spray head movement between said normal and adjustment positions.
Claim 36
Dependent Claim
68 words
The rotary drive sprinkler of claim 32 further including spring means for urging said drive sleeve toward said normal position, primary seal means for preventing leakage between said riser and said drive sleeve when said drive sleeve is in said normal position, and secondary seal means acting between said riser and said drive sleeve to substantially prevent leakage therebetween when said drive sleeve is in said adjustment position.
Claim 37
Dependent Claim
38 words
The rotary drive sprinkler of claim 33 wherein said secondary seal means comprises a generally annular pressure-responsive seal interposed between said riser and drive sleeve, said seal including orifice means permitting relatively small leakage flow across said seal.
Claim 38
Dependent Claim
27 words
The rotary drive sprinkler of claim 33 wherein said spray head and said drive sleeve include snap-fit means for locking said spray head onto said drive sleeve.
Claim 39
Dependent Claim
24 words
The rotary drive sprinkler of claim 35 further including a drive lug on said drive sleeve for rotational driving engagement with said spray head.
Claim 40
Dependent Claim
92 words
The rotary drive sprinkler of claim 10 wherein said spray head comprises a pop-up spray head also movable between a retracted position substantially within said housing and a spraying position extending above said housing, said housing having a removable cap with an opening therein for movement of said spray head between said retracted and spraying positions, and further including a resilient seal member surrounding the cap opening and sealingly engaging said spray head, said seal member having an enlarged flange for overlying and sealing the juncture between said housing and said cap.
Claim 41
Dependent Claim
35 words
The rotary drive sprinkler of claim 23 including means for releasably detenting said trip ring relative to said drive ring when said stops are in an adjustment position with their stop surfaces disposed substantially face-to-face.
Claim 42
Dependent Claim
247 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a pop-up stem assembly including a spray head for outward projection of an irrigation water stream, said stem assembly being movable between a retracted position with said spray head substantially within said housing and a spraying position with said spray head elevated above said housing, said stem assembly further including a drive sleeve rotatably supporting said spray head with respect to said housing; a rotary drive assembly movable with said stem assembly between said retracted and spraying positions, said rotary drive assembly including a drive case mounted against rotation within said housing and water-driven means for rotatably driving said drive sleeve; first and second stops rotatable with said drive sleeve; reverse means movable between forward- and reverse-drive positions for reversing the direction of rotational driving of said spray head by said drive sleeve; and a resilient trip member extending from said reverse means to a position engageable with said first and second stops upon spray head rotation, said first stop being shaped for moving said trip member to switch said reverse means upon forward spray head rotation and to permit trip member passage without switching said reverse means upon reverse spray head rotation, and said second stop being shaped for moving said trip member to switch said reverse means upon reverse spray head rotation and to permit trip member passage without switching said reverse means upon forward spray head rotation.
Claim 43
Dependent Claim
247 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a pop-up stem assembly including a spray head for outward projection of an irrigation water stream, said stem assembly being movable between a retracted position with said spray head substantially within said housing and a spraying position with said spray head elevated above said housing, said stem assembly further including a drive sleeve rotatably supporting said spray head with respect to said housing; a rotary drive assembly movable with said stem assembly between said retracted and spraying positions, said rotary drive assembly including a drive case mounted against rotation within said housing and water-driven means for rotatably driving said drive sleeve; first and second stops rotatable with said drive sleeve; reverse means movable between forward- and reverse-drive positions for reversing the direction of rotational driving of said spray head by said drive sleeve; and a resilient trip member extending from said reverse means to a position engageable with said first and second stops upon spray head rotation, said first stop being shaped for moving said trip member to switch said reverse means upon forward spray head rotation and to permit trip member passage without switching said reverse means upon reverse spray head rotation, and said second stop being shaped for moving said trip member to switch said reverse means upon reverse spray head rotation and to permit trip member passage without switching said reverse means upon forward spray head rotation.
Claim 44
Dependent Claim
34 words
The rotary drive sprinkler of claim 39 wherein said first and second stops comprise an arcuately spaced pair of stops having stop surfaces facing each other and ramped surfaces facing away from each other.
Claim 45
Dependent Claim
20 words
The rotary drive sprinkler of claim 39 including means for adjusting the arcuate spacing between said first and second stops.
Claim 46
Dependent Claim
114 words
The rotary drive sprinkler of claim 39 wherein said first stop is carried by a drive ring rotatable with said spray head and said second stop is carried by a trip ring releasably carried by said drive ring, and further including means supporting said spray head and said drive ring for movement relative to said rotary drive assembly between a normal operating position with said trip ring rotating with said drive ring and an adjustment position with said trip ring locked against rotation with said drive ring, said spray head and said drive ring beng rotatable relative to said trip ring when in said adjustment position to adjust the arcuate spacing between said stops.
Claim 47
Dependent Claim
40 words
The rotary drive sprinkler of claim 42 further including lock means for locking said spray head and said drive ring in their normal position relative to said rotary drive assembly thereby preventing adjustment of the arcuate spacing between said stops.
Claim 48
Dependent Claim
17 words
The rotary drive sprinkler of claim 42 wherein said trip ring is ratcheted about said drive ring.
Claim 49
Dependent Claim
47 words
The rotary drive sprinkler of claim 42 further including a drive case for said rotary drive means and supported against rotation within said sprinkler housing, said trip ring and said drive case including interengageable means for locking said trip ring against rotation when in said adjustment position.
Claim 50
Dependent Claim
23 words
The rotary drive sprinkler of claim 42 further including means for biasing said spray head and said drive ring toward their normal position.
Claim 51
Dependent Claim
393 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a pop-up stem assembly mounted within said housing for movement between a retracted position substantially within said housing and a spraying position with a spray head thereon elevated above said housing for spraying irrigation water outwardly therefrom, said stem assembly further including a drive sleeve rotatably carrying said spray head; a rotary drive assembly for rotatably driving said drive sleeve and said spray head in a succession of small rotational steps, said rotary drive assembly including a drive case nonrotationally supported within said housing, at least one water-driven turbine and means responsive to turbine rotation for driving said drive sleeve in a succession of small rotational steps; reverse means for reversing the direction of rotation of said turbine, said reverse means including a swirl plate having at least two oppositely angled swirl ports for passage of water in opposite swirl directions in driving relation with said turbine; means for directing a drive jet generally toward said turbine, said swirl plate being movable between a forward- and reverse-drive position with said swirl ports aligned respectively with said drive jet; a resilient trip wire anchored at one end to said swirl plate for movement therewith and extending outwardly therefrom; a first stop carried by drive ring; and a second stop carried by a trip ring releasably carried in turn about said drive ring; said first stop being shaped for moving said trip wire to switch said swirl plate upon forward turbine rotation and to permit passage of said trip wire without switching said swirl plate upon reverse turbine rotation, said second stop being shaped for moving said trip wire to switch said swirl plate upon reverse turbine rotation and to permit passage of said trip wire without switching said swirl plate upon forward turbine rotation; said drive sleeve and spray head being further movable relative to said drive case in the direction of movement between said retracted and spraying positions for movement between a normal operating position with said trip ring rotating with said drive ring and an adjustment position with said trip ring locked against rotation with said drive ring, said spray head and said drive ring being rotatable relative to said trip ring when in said adjustment position to adjust the arcuate spacing between said stops.
Claim 52
Dependent Claim
393 words
A rotary drive sprinkler, comprising: a sprinkler housing adapted for connection to a supply of irrigation water; a pop-up stem assembly mounted within said housing for movement between a retracted position substantially within said housing and a spraying position with a spray head thereon elevated above said housing for spraying irrigation water outwardly therefrom, said stem assembly further including a drive sleeve rotatably carrying said spray head; a rotary drive assembly for rotatably driving said drive sleeve and said spray head in a succession of small rotational steps, said rotary drive assembly including a drive case nonrotationally supported within said housing, at least one water-driven turbine and means responsive to turbine rotation for driving said drive sleeve in a succession of small rotational steps; reverse means for reversing the direction of rotation of said turbine, said reverse means including a swirl plate having at least two oppositely angled swirl ports for passage of water in opposite swirl directions in driving relation with said turbine; means for directing a drive jet generally toward said turbine, said swirl plate being movable between a forward- and reverse-drive position with said swirl ports aligned respectively with said drive jet; a resilient trip wire anchored at one end to said swirl plate for movement therewith and extending outwardly therefrom; a first stop carried by drive ring; and a second stop carried by a trip ring releasably carried in turn about said drive ring; said first stop being shaped for moving said trip wire to switch said swirl plate upon forward turbine rotation and to permit passage of said trip wire without switching said swirl plate upon reverse turbine rotation, said second stop being shaped for moving said trip wire to switch said swirl plate upon reverse turbine rotation and to permit passage of said trip wire without switching said swirl plate upon forward turbine rotation; said drive sleeve and spray head being further movable relative to said drive case in the direction of movement between said retracted and spraying positions for movement between a normal operating position with said trip ring rotating with said drive ring and an adjustment position with said trip ring locked against rotation with said drive ring, said spray head and said drive ring being rotatable relative to said trip ring when in said adjustment position to adjust the arcuate spacing between said stops.
Claim 53
Dependent Claim
17 words
The rotary drive sprinkler of claim 47 wherein said rotary drive assembly comprises a ball drive assembly.
Claim 54
Dependent Claim
40 words
The rotary drive sprinkler of claim 47 further including lock means for locking said spray head and said drive ring in their normal position relative to said rotary drive assembly thereby preventing adjustment of the arcuate spacing between said stops.
Claim 55
Dependent Claim
71 words
The rotary drive sprinkler of claim 49 wherein said pop-up stem assembly further includes a riser secured to and upstanding from said drive case about said drive sleeve and spray head to define an open annular recess when said spray head and drive ring are in the normal position, said lock means comprising a lock ring seated within said recess to prevent movement of said spray head to said adjustment position.
Claim 56
Dependent Claim
17 words
The rotary drive sprinkler of claim 47 wherein said trip ring is ratcheted about said drive ring.
Claim 57
Dependent Claim
21 words
The rotary drive sprinkler of claim 51 further including means for vertically supporting said trip ring relative to said drive ring.
Claim 58
Dependent Claim
24 words
The rotary drive sprinkler of claim 47 further including spring means for biasing said spray head and said drive ring toward their normal position.
Claim 59
Dependent Claim
144 words
The rotary drive sprinkler of claim 47 wherein said spray head includes a nozzle having at least one orifice formed therein of selected size, and further including water flow regulation means having at least one drive jet nozzle for passage of a first portion of the water connected to said housing into driving relation with said turbine and then to said spray head, a first bypass port including a pressure compensating valve, and a second bypass port including a flow control bushing with an open flow opening therein of selected size in accordance with the size of said spray head nozzle orifice, said first and second bypass ports being for bypass passage of a second portion of the water around said turbine to said spray head, said jet nozzle and said first and second bypass ports being in parallel flow relation with each other.
Claim 60
Dependent Claim
20 words
The rotary drive sprinkler of claim 54 further including hood means for diverting said second portion away from said turbine.
Claim 61
Dependent Claim
15 words
The rotary drive sprinkler of claim 47 wherein said trip wire includes an intermediate loop.
Claim 62
Dependent Claim
18 words
The rotary drive sprinkler of claim 47 wherein said second stop is resiliently carried by said trip ring.
Claim 63
Dependent Claim
111 words
The rotary drive sprinkler of claim 51 wherein said trip ring includes a pawl engageable with ratchet teeth on said drive ring, said stops each having a generally upright stop surface for engagement with said trip wire to switch the position of said swirl plate and a ramped surface for engagement with said trip wire without switching the position of said swirl plate, said drive ring beng movable relative to said trip ring to adjust said first and second stops to a full-circle position with their stop surfaces disposed substantially face-to-face, said pawl being releasably seatable within a detent in said drive ring when said stops are in said full-circle position.
Claim 64
Dependent Claim
57 words
The rotary drive sprinkler of claim 50 further including primary seal means for preventing leakage between said riser and said drive sleeve when said drive sleeve is in said normal position and secondary seal means acting between said riser and said dirve sleeve to substantially prevent leakage therebetween when said drive sleeve is in said adjustment position.
Claim 65
Dependent Claim
76 words
The rotary drive sprinkler of claim 59 wherein said secondary seal means comprises a seal ring interposed between said drive sleeve and riser and having a generally U-shaped cross section opening in an upstream direction, and a seal water interposed between said drive sleeve and riser on the downstream side of said seal ring, said seal ring and seal washer cooperatively defining an elongated leakage path for a small leakage flow across said secondary seal means.